1. Field of the Invention
The invention relates to a working machine, such as an industrial truck, having a spring-loaded brake. The brake has a braking position and a release position, and can be controlled by means of a brake valve producing a brake-release pressure.
2. Technical Considerations
In the case of mobile working machines in the form of industrial trucks, a spring-loaded brake is provided, which is used as a parking brake. Using the spring-loaded brake, which is acted upon in the braking position, the industrial truck can be kept at a standstill on slopes or in the case of a traction drive which is not being driven. During driving of the industrial truck, the spring-loaded brake is acted upon so as to be brought into the release position. The spring-loaded brake is, in this case, acted upon by means of a spring so as to be brought into the braking position and can be acted upon by means of a brake-release pressure produced by a pressure medium source, counter to the force of the spring, so as to be brought into the release position.
A generic working machine in the form of an industrial truck and having a spring-loaded brake used as a parking brake is shown in DE 197 52 022 A1, herein incorporated by reference.
With such working machines, a service brake is also necessary, with which metered braking of the industrial truck can be achieved by an operator when actuating a service brake input device. In known working machines, in addition to the spring-loaded brake, a separate service brake, for example a mechanical or hydraulic service brake, is provided for this purpose, which results in a high degree of complexity in terms of design for the service brake.
Therefore, it is an object of the present invention to provide a working machine of the generic type mentioned initially but which can be provided with a service brake with less complexity in terms of design, which service brake has good metering capability.